The present invention relates generally to catheters. More particularly, the present invention relates to catheters that are designed to permit a guide wire or other structure to be fed laterally from the region of an expandable working element. Such arrangements are believed to be particularly useful in devices that are intended for use in the vicinity of vessel bifurcations.
Catheters are used in a very wide variety of medical procedures. Typically catheters are relatively long and flexible. Many times, (as for example in many vascular applications) the catheter may need to be inserted into a relatively tortuous vessel. Since it can be difficult to steer many types of catheters, guide wires are often used to position the catheters. Guide wires are typically formed from a very small diameter wire having a flexible tip that may be bent (typically pre-bent) by a physician to facilitate “steering” the guide wire to a desired location through a potentially tortuous path such as the vasculature.
In some applications the targeted region of a vessel may be at a location where the vessel bifurcates. For example, in cases where atherosclerotic plaque has developed in the region of a vascular vessel bifurcation, it may be desirable to perform a therapeutic treatment on the affected vessels. For example, in some applications, it may be desirable to stent one or both branches of a vessel bifurcation. In other applications, it may be desirable to perform an operation such as angioplasty or atherectomy in one branch, while stenting the other branch. In many such applications, it may be desirable to be able to position guidewires in both the main and the side branch of the bifurcation or to position a wire in the side branch when a balloon is already inserted into the main branch.
In situations where the main or side branch has been stented and the stent is positioned over the bifurcation it might be difficult to pass a wire through the stent structure for treating the other vessel, if desired. This is due, in part, to the fact that the angle between the two branches can be relatively large. In most bifurcations the vessels branch at a bifurcation angle of less than 60 degrees, but there are also vessel bifurcations in which the bifurcation angles are in the range of 60-90 degrees and sometimes even greater. Especially in cases where the bifurcation angle is greater than 60 degrees it can be difficult to pass a stent after implantation.
When treating a bifurcation it is important for the physician to be able to easily access the second vessel. Depending on the nature of the stenosis it might be possible that plaque shifting occurs during the treatment. This can occur when one of the vessels is dilated with a balloon or a stent is placed. Plaque shifting (which is sometimes referred to as the “snowplow effect” may then occlude (or partially occlude) the other vessel. To re-open the vessel, first a guide wire has to be placed in the second vessel. Depending on the lesion, the physician might decide to dilate the second vessel with a balloon catheter or place another stent.
Although there are currently a number of devices that are designed for use in the region of vessel bifurcations, there are continuing efforts to provide improved mechanisms for positioning a guidewire and/or appropriate working devices in the non-treated vessel of a bifurcation.